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B. DEMONT. AIR cooLED ExPLosloN ENGINE.

APPLICATIN FILED OCT- 15. |918.

, Patented Dec. 23, 1919.

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BENOIT DEMONT, 0F PARIS, lERAlSl'CE.V

AIR-COOLED EXPLOSION-ENGINE.

Specification of Letters Patent.

Patented Dec. 23, 1919.

Application filed October 15, 1918. Serial No. 258,222.

To all whom it may concern:

Be it known that I,BEN01T DEMONT, a citizen of the Republic of France, and a resident of 141 Avenue Malakoif, Paris, France, have invented new and useful Improvements in Air-Cooled Explosion-Engines, of which the following isa specication.

The present invention relates to a doubleacting air-cooled explosion engine, which has as large as possible cooling surface for the minimum bulk or size.

This engine is characterized by the combination of a piston having upon its two faces, central rentrant portions of different diameters forming interior tubular passages reentering one interiorly o-f the other, and of a cylinder having upon its heads central reentrant portions of correspondingly different diameters also forming interior tubular passages rentering one interiorly of the other, the piston and the cylinder thus having each an exterior annulanportion surrounding a central tubular portion formed on two tubes rentering one interiorly of the other.

It has already been proposed to form upon the heads of cylinders central tubular rentrant portions in which can enter corresponding tubular prolongations of the piston; but the central tubular portions of the two faces of the cylinder, or 'of the piston, were not of different diameters and did not enter one interiorly of the other, that is to say were not boxed one in the other as is the case in the present invention which arrangement enables the engine to be of greatly reduced dimensions in the longitudinal direction.

The annexed drawing represents in axial transverse section, one way of carrying out the present invention by way of example.

The exterior head al of the cylinder a has a central part a2 rentering interiorly in such a way as to form a central tubular passage arranged interiorly of an annular portion; this tubular passage is open at its exterior extremity and is provided at its inner extremity with a reinforcing wall a3, perforated with holes or openings a4.

The 'head al of the cylinder has also a central portion a2 rentering toward the interior and forming a central tubular passage; this passage is of a diameter greater than that of the tubular passage a2 so that laterally it extends exteriorly in relation thereto.

The piston b on its exterior face 61 also has a central portion b2 rentering inwardly and forms a tubular passage, open at its two extremities and capable of sliding with light friction around and exteriorly of the tubular passage a2. Further, the face bl of the piston has a central portion 52 rentering toward the interior and forming a tubular' passage of a diameter greater than that of the tubular passage b2 and capable of sliding with light friction around and exteriorly of the tubular passage a2 of the cylinder.

The piston thus comprises between the faces b, bl and the tubular passage 1)2, an annular exterior portion arranged around a tubular central portion formed by the two tubes b2 2)2 rentering one interiorly of the other. The same arrangement is effected in the cylinder.

The central portion b2 of the piston is connected at b3 to'the piston rod o. Packing rings, piston-rings or the like a5 1;5 are arranged near the interior extremity of each of the ree'ntrant central portions a2 and a2 of the cylinder a, as well as upon the exterior surface of the piston?) at b4. A wearing piece in the form of a liner d is preferably arranged within the cylinder 0:.

The arrangement of the present invention enables to be obtained with a very small bulk of the motor, a very large surface for aircooling. This cooling is further increased by a double circulation of air (see the arrows) a current of air passes in the longitudinal axial direction of the engine to the interior of the tubular passages az and a2 by the openings or apertures b5 formed in the wall of the tubular central portion b2 of the piston, and by the openings or holes a* in the partition a3; a second current of air traverses the motor in the transverse direction from the interior toward the exterior, passing from the central portion into the exterior annular portion of the piston b by means of openings Z2 formed in the interior wall 52 of the piston, by openings b? in its exterior wall, and escapes to the exterior by the holes or apertures a and d1 formed respectively in the cylindrical body a and in the wearing piece d.

Having now particularly described and ascertained the nature of my said invention and in what manner the same is to be per formed, I declare that what I claim is 1. In a double-acting air-cooled explosion engine, the combination with a piston having on its two faces rentrant central portions of dierent diameters forming interior tubular passages rentering one interiorly of the other, of a cylinder having` upon its heads, rentrant central portions or correspondingiy different diameters also forming interior tubular passages rentering one interiorly of the other,the piston and the cylinder thus having' each an exterior annular portion surrounding a tubular central portion formed of two tubes reenter-ing one nteriorly of the other.

2. In a construction such as specified in claim l, ports in the piston and cylinder exterior through the piston and the cylinder.

In testimony whereof I have signed my 20 name to this specification.

BENOIT DEMONT.

Witnesses CHARLES IRVING, F. DEFVRIMONT, 

